Power transistors provide a high power gain and may dissipate up to 100 watts or more. Some power transistors have a vertical structure. In a vertical power metal-oxide-semiconductor field-effect-transistor (MOSFET), the voltage rating of the transistor is a function of the doping and thickness of the epitaxial layer and the current rating is a function of the channel width. This makes it possible for the transistor to sustain both high blocking voltage and high current within a compact piece of semiconductor material.
Typically, vertical power transistors have two contact elements on one face and one contact element on an opposing face. In the on state, current flows from one face to the other face. A vertical power MOSFET, usually, has source and gate contact elements on one face and a drain contact element on the other face. The vertical power MOSFET exhibits an on resistance between the drain and source terminals, where the resistance of the epitaxial layer is a primary factor in the on resistance of the transistor. Manufacturing a thin vertical power MOSFET is one way of decreasing the on resistance of the transistor.
Often, packaging semiconductor chips includes both front-end processing and back-end processing. In front-end processing, semiconductor chips can be manufactured or expanded to accommodate all of the contact elements. In back-end processing, leads can be distributed to fit a footprint on a printed circuit board.
For these and other reasons there is a need for the present invention.